A K-Band Power Amplifier with 26-dBm Output Power and 34% PAE with Novel Inductance-based Neutralization in 90-nm CMOS

A fully-integrated K-band transformer combined power amplifier (PA) with novel neutralization technique is presented and implemented in 90-nm CMOS technology for 5G and 24-GHz ISM-band applications. Four single-stage cascode cells are combined with transformers as two differential amplifier cells. Current-combining topology is used to combine the two differential amplifier cells to increase output power. The asymmetrical transformers are designed to compensate phase imbalance. The novel inductance-based neutralization structure is utilized to cope with the overall stability issue. Thus, the optimal transistor sizes can be chosen to achieve high output power and power added efficiency (PAE). The measurement results demonstrate 16.3-dB small-signal gain, saturated power (Psat) of 26.0 dBm, output 1-dB compression point (OP
_1dB
) of 23.2 dBm, and peak PAE of 34% at 28 GHz. The chip size with all pads is 0.401 mm
²
. To the authors' knowledge, this circuit demonstrates a superior output power and PAE performance compared with the reported K-band CMOS PAs.